Photo taken on Aug. 16, 2019 shows the main chimney of Amager Bakke Incinerator Plant in Copenhagen, Denmark. Copenhill, a new artificial ski slope built on the roof of a huge waste incinerator here, was opened to the public on Friday. While the public can whizz down the 450-meter ski slope, up to 450,000 tonnes of waste will continue to be converted annually into heat and electricity in Amager Bakke Incinerator Plant underneath skiing guests' feet. (Xinhua/Lin Jing)